Chapter 16: Composites

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1 Chapter 16: Coposites ISSUS TO ADDRSS... What are the classes and types o coposites? What are the advantages o using coposite aterials? How do we predict the stiness and strength o the various types o coposites? 1

2 Coposite Cobination o two or ore individual aterials Design goal: obtain a ore desirable cobination o properties (principle o cobined action) e.g., low density and high strength 2

3 Terinology/Classiication Coposite: -- Multiphase aterial that is artiicially ade. Phase types: -- Matrix - is continuous -- Dispersed - is discontinuous and surrounded by atrix Adapted ro Fig. 16.1(a), Callister & Rethwisch 8e. 3

woven ibers cross section view 0.5 0.5 CMC: increase K Ic PMC: increase, s y, TS, creep resist.

4 Terinology/Classiication Matrix phase: -- Purposes are to: - transer stress to dispersed phase - protect dispersed phase ro environent -- Types: MMC, CMC, PMC etal ceraic polyer Dispersed phase: -- Purpose: MMC: increase s y, TS, creep resist. woven ibers cross section view CMC: increase K Ic PMC: increase, s y, TS, creep resist. -- Types: particle, iber, structural Reprinted with perission ro D. Hull and T.W. Clyne, An Introduction to Coposite Materials, 2nd ed., Cabridge University Press, New York, 1996, Fig. 3.6, p

5 Classiication o Coposites Stier particulate bears raction o load, restrain atrix oveent in vicinity Adapted ro Fig. 16.2, Callister & Rethwisch 8e. Sall dispersed particles ipede otion o dislocations 5

6 For which particle reinorced coposite would bond strength be ore iportant? What geoetric/spatial properties o particles in dispersed phase would inluence perorance? 6

Particle-reinorced Fiber-reinorced Structural Classiication: Particle-Reinorced (i) xaples: - Spheroidite steel

19, Callister & Rethwisch 8e. (Fig. 10.19 is copyright United States Steel Corporation, 1971.

4, Callister & Rethwisch 8e. (Fig. 16.4 is courtesy Carboloy Systes, Departent, General lectric Copany.

7 Particle-reinorced Fiber-reinorced Structural Classiication: Particle-Reinorced (i) xaples: - Spheroidite steel atrix: errite (a) (ductile) 60 particles: ceentite ( Fe 3 C ) (brittle) Adapted ro Fig , Callister & Rethwisch 8e. (Fig is copyright United States Steel Corporation, 1971.) - WC/Co ceented carbide atrix: cobalt (ductile, tough) : 600 particles: WC (brittle, hard) Adapted ro Fig. 16.4, Callister & Rethwisch 8e. (Fig is courtesy Carboloy Systes, Departent, General lectric Copany.) - Autoobile tire rubber atrix: rubber (copliant) 0.75 particles: carbon black (sti) Adapted ro Fig. 16.5, Callister & Rethwisch 8e. (Fig is courtesy Goodyear Tire and Rubber Copany.) 7

8 Particle-reinorced Fiber-reinorced Structural Classiication: Particle-Reinorced (ii) Concrete gravel + sand + ceent + water - Why sand and gravel? Sand ills voids between gravel particles Reinorced concrete Reinorce with steel rebar or reesh - increases strength - even i ceent atrix is cracked Prestressed concrete - Rebar/reesh placed under tension during setting o concrete - Release o tension ater setting places concrete in a state o copression - To racture concrete, applied tensile stress ust exceed this copressive stress Posttensioning tighten nuts to place concrete under copression nut threaded rod 8

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10 Particle-reinorced Fiber-reinorced Structural Classiication: Particle-Reinorced (iii) lastic odulus, c, o coposites: -- two rule o ixture extrees: upper liit: c = V + V p p Data: Cu atrix w/tungsten particles (GPa) lower liit: 1 = V + V p c p Adapted ro Fig. 16.3, Callister & Rethwisch 8e. (Fig is ro R.H. Krock, ASTM Proc, Vol. 63, 1963.) (Cu) ( W) vol% tungsten Application to other properties: -- lectrical conductivity, s e : Replace s in equations with s e s. -- Theral conductivity, k: Replace s in equations with k s. 10

11 Particle-reinorced Fiber-reinorced Structural Classiication: Fiber-Reinorced (i) Fibers very strong in tension Provide signiicant strength iproveent to the coposite x: iber-glass - continuous glass ilaents in a polyer atrix Glass ibers strength and stiness Polyer atrix holds ibers in place protects iber suraces transers load to ibers 11

12 Particle-reinorced Fiber-reinorced Structural Classiication: Fiber-Reinorced (ii) Fiber Types Whiskers - thin single crystals - large length to diaeter ratios graphite, silicon nitride, silicon carbide high crystal perection extreely strong, strongest known very expensive and diicult to disperse Fibers polycrystalline or aorphous generally polyers or ceraics x: aluina, araid, -glass, boron, UHMWP Wires etals steel, olybdenu, tungsten 12

13 Longitudinal direction Fiber Alignent Adapted ro Fig. 16.8, Callister & Rethwisch 8e. Transverse direction aligned continuous aligned rando discontinuous 13

14 Particle-reinorced Fiber-reinorced Structural Classiication: Fiber-Reinorced (v) Critical iber length or eective stiening & strengthening: iber ultiate tensile strength s iber length 2 d c iber diaeter shear strength o iber-atrix interace x: For iberglass, coon iber length > 15 needed For longer ibers, stress transerence ro atrix is ore eicient Short, thick ibers: s iber length 2 d c Long, thin ibers: s iber length 2 d c Low iber eiciency High iber eiciency 14

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17 Coposite Stiness: Longitudinal Loading Continuous ibers - stiate iber-reinorced coposite odulus o elasticity or continuous ibers Longitudinal deoration s c = s V + s V and c = = volue raction isostrain cl = V + V cl = longitudinal odulus c = coposite = iber = atrix 17

18 Coposite Stiness: Transverse Loading In transverse loading the ibers carry less o the load c = V + V and 1 ct V V ct V V s c = s = s = s isostress ct = transverse odulus c = coposite = iber = atrix 18

19 xaple 16.1 A continuous and aligned glass iber-reinorced coposite consists o 40 % vol o glass ibers having an elastic odulus o 69 Gpa and 60 % vol o a polyester resin that, when hardened, displays a odulus o 3.4 Gpa. a. Copute the elastic odulus o the coposite in the longitudinal direction b. I the cross-sectional area is 250 2, and a stress o 50 Mpa is applied in this longitudinal direction, copute the agnitude o the load carried by each o the iber and atrix phases. c. Deterine the strain that is sustained by each phase when the stress in part (b) is applied.

20 ???? ? coposite - reinorced iber glass continuous and aligned - : Proble stateent 2 al longitudin c cl F F Mpa A Gpa Gpa V V s

21 kn F kn F F F Gpa A F F F V V F F V V cl c c cl : and in Using the two equations 30 Solution : Theory : s

22 Solution : / / / / Theory : c c A V F A F A V F A F s s

23 xaple 16.2 Copute the elastic odulus o the coposite aterial in exaple 16.1, but assue that the stress is applied perpendicular to the direction o iber alignent.

24 Proble stateent : - continuous and aligned glass iber - reinorced coposite V V ct Gpa 3.4Gpa? Theory : ct ct V Solution : V 5.5Gpa

25 Particle-reinorced Fiber-reinorced Structural Coposite Stiness stiate o cd or discontinuous ibers: -- valid when iber length < 15 s d c -- lastic odulus in iber direction: cd = V + K V eiciency actor: -- aligned: K = 1 (aligned parallel) -- aligned: K = 0 (aligned perpendicular) -- rando 2D: K = 3/8 (2D isotropy) -- rando 3D: K = 1/5 (3D isotropy) Values ro Table 16.3, Callister & Rethwisch 8e. (Source or Table 16.3 is H. Krenchel, Fibre Reinorceent, Copenhagen: Akadeisk Forlag, 1964.) 25

26 Particle-reinorced Fiber-reinorced Structural Coposite Strength stiate o * s cd or discontinuous ibers: 1. When l > l c * * s cd s V 1 l c s (1V ) 2 l 2. When l < l c * l c d V s (1V ) s c d 26

27 Particle-reinorced Fiber-reinorced Structural Classiication: Structural Lainates - -- stacked and bonded iber-reinorced sheets - stacking sequence: e.g., 0º/90º - beneit: balanced in-plane stiness Sandwich panels -- honeycob core between two acing sheets - beneits: low density, large bending stiness Adapted ro Fig , Callister & Rethwisch 8e. ace sheet adhesive layer honeycob Adapted ro Fig , Callister & Rethwisch 8e. (Fig is ro ngineered Materials Handbook, Vol. 1, Coposites, ASM International, Materials Park, OH, 1987.) 27

28 Coposite Beneits CMCs: Increased toughness Force particle-rein un-rein iber-rein Bend displaceent MMCs: Increased creep resistance ss (s -1 ) Al (GPa) 6061 Al w/sic whiskers PMCs: Increased /r PMCs ceraics etal/ etal alloys polyers Density, r [g/ 3 ] Adapted ro T.G. Nieh, "Creep rupture o a silicon-carbide reinorced aluinu coposite", Metall. Trans. A Vol. 15(1), pp , Used with perission. s (MPa) 28

29 Suary Coposites types are designated by: -- the atrix aterial (CMC, MMC, PMC) -- the reinorceent (particles, ibers, structural) Coposite property beneits: -- MMC: enhanced, s, creep perorance -- CMC: enhanced K Ic -- PMC: enhanced /r, s y, TS/r Particulate-reinorced: -- Types: large-particle and dispersion-strengthened -- Properties are isotropic Fiber-reinorced: -- Types: continuous (aligned) discontinuous (aligned or rando) -- Properties can be isotropic or anisotropic Structural: -- Lainates and sandwich panels 29

30 ANNOUNCMNTS Reading: Core Probles: 16.10, 16.11,

Chapter 16: Composites

Chapter 16: Composites ISSUES TO ADDRESS... What are the classes and types of composites? What are the advantages of using composite materials? How do we predict the elastic modulus for composites with